Drying printing inks



April 16, 1940.

As. ENGLE DRYING PRINT-ING INKs Filed Sept. l1, 1937 INVENTOR ATTO EYdesired temperature by Patented Apr. 16, 1940 PATENT OFFICE alarmsDBYING PRINTING :Nxs

Loy S. Engle, Harrlngtonlark, N. J., assl'gnor to InterchemicalCorporation, New York, N. Y., a

corporation o! Ohio Application septembeii1, 1937, serial No. 163,350

4 claims.` (on 3424) 'I-'his invention relates to printing-and hasparticular reference to a new and novel method of drying printing inkcontaining a diicultly volatilizable solvent. More particularly, mymethod 5 contemplates passing the prints through a hot bath of inertmaterial, such as molten metal, to drive oif the solvents from the ink.

Recently, a new type of printing ink has been introduced into theprinting art. These inks lo comprise dispersions of pigments in vehiclesconsisting of plastic to solid binders, dissolved in solvents which aresubstantially non-evaporating at ordinary press-room temperatures, butwhich evaporate at elevated temperatures. Prints of 16 these inks. areordinarily dried either by passing them over a drum heated to a veryhigh temperature orby subjecting them to very high tem-` peratures, ofthe' order of 1000 F. to 2000 F. for

ra few seconds. Flashing and burning of the ink vapors have likewise.been resorted to in order to improve the drying of such inks.

In order to obtain high press speeds with these methods, the heatapplied to the paper must be considerably higher than. that actuallyrequired to dry the ink, since the paper passes the heat at such speedsthat the prints neverattain maxil.

mum temperature. Because of the use of Such high heats, there is alwaysdanger that thel paperv vused will`scorch,`where unusual conditions pernmit of the/ development of too high aheat at some spot on the paper.This is particularly true with heat-sensitive stocks, such as breadwrapper paper, which scorches as low as 200 C.

I have discovered a new and novel method of printingpaper with such inkswithout danger of scorching,.which comprises passing the printed paperthrough a bath of inert fluid heated to a temperature suiciently high tocause rapid vaporization of the solvent, but below the scorchw ingpointof the paper. The paper thus attains 'a maximum temperature above whichit cannot rise, thus eliminating the danger of scorching.

'The huid must be substantially non-volatile at the high temperaturesused (in the neighborhood o f 150 C. to 200 C.) must not affect the inkorA the paper, and preferably be cheapand easy to heat. The metals areparticularly suitable fromall points of yview; and I prefer to use lowmelting metals and alloys, such as wood metal (1W. P.

65.5 C.) as the heating bath.

The diagrammatic drawing attached. hereto is A illustrative of theprocess. A. web of paper I, which bears a wet print, passes under aroller 2 into'a bath of molten metal I, maintained at the burners l. Themolten scorching point of the paper,

, quires a minimum metal is kept at a uniform temperature by any knownthermostatlc device, indicated at 5'. The paper web passes under roll `6and nally out under roll 1, then over cooling rolls 8 and 9, to arewind. As can be seen from the drawings, the I rollers 2, 0 and 1 arepreferably journalled above the bath to prevent the possibility ofcontact between molten metal and the roll shaft bearings.

As the paper passes through the bath, 'it rapidly reaches thetemlwxature"` of the bath, owing' l to the excellent heat transfer ofthe metal. The solvent evaporates into the bath, and rises to ifssurface, from whence it is exhausted up a stack I0.

. The metal is of the paper by a doctor blade I I, which wipes the backside clean just as it emerges from the bath. Anypmetal clinging to theprinted sideof the paper is removed either by centrifugal force whilevpassing about the roll 1 at a high speed, while 20 molten,or by gra tyand centrifugal force while going about the cooling roller 9, after themetal has set a solid. Such metal is collected in a box I2, placed underthe roller.

By the use of my method, the bath may be 2B heated up to `temperatureswithin 10 C. of the with assurance that the paper will not be damaged.This heating re time, because of the high rate of heat transfer of themetal, so that' complete $0 drying maybe obtained with press-stableinks, by keeping the web immersed in the bath for as short a time as 2to 3 seconds.

As indicated above, I prefer to operate at as high a temperature aspossible, while running no a5 danger of scorching the paper. With moreheatsensitive stocks, such as Scorch at 200 C to 220 C., I prefer tooperate at 180 C. to 200 C.; with less Asensitive stocks (scorching at250 C. to 300 C.), temperaturesl of225 C. to 240 C. may be o used. i

While my method is particularly applicable to printing inks containingdiiiicultly volatilizable solvents, it is likewise applicable toprinting inks containing polymerizable synthetic resins and 5 the likewhich are set largely by heat, as my method provides for the applicationof maximum heat to the prints without danger of scorching.

What YI claim is:

l. .The method of drying prints of prntinglm` inks containing solventswhich are substantially non-volatile at 20 C. but which evaporaterapidly at 150 C., which comprises passing the prints through abath ofan inert fluid heatedto a temperature of the order of 150 C. or higherthe 5| removed from the unprinted side 13' passage through the bathbeing completed in a few seconds.

2. The method of drying wet mms containing solvents which aresubstantialiv non-volatile at 20 C. but which evaporate rapidly attemperatures of the order o1' 150 C. on paper carrying such lms, whichcomprises passing the paper through a bath of uid metal heated to atemperature of at least the order o1' 150 C., but below the scorchingpoint of the paper, the passage through the bath being completed in afew seconds.

3. 'I'he method of frying wet ilims containing solvents which aresubstantially non-volatileat 20 C. but which evaporate rapidly attemperatures of the order of 150 C. on paper carrying such films, whichcomprises passing the paper through a. bath of iiuid metal heated to atem-` perature of at least the order of 150 C., but be-l low thescorching point of the paper, the passage through the bath being in afew marked side of the, paper with after it emerges from the bath.

solvents which are. substantially non-volatile at seconds, and removingthe metal from the unfY a doctor imite- 4. The method of -drying wet lmscontaining tures of the order of150 C. on papercarrymg such mms, whichcomprises passing the paper through a bath of fluid metal lheated to atemperature of at least theorder of 150 C.;

-low the scorching point of the the pssagq through the bath beingcompleted'in a few seconds, removing the metal froxnthe side of thepaper withY a Adoctor knife after it emerges Afrom the bath,` and fromthe marked Asideby4 gravity and 1 by centrifugal applied tothepapenr, 1

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